and in afghanistan, a group of american soldiers took this day to reenlist. general david petraeus is about to become the next cia director, and was there to say goodbye and thanks. >> and america can never thank you enough. >> reporter: america's 235th birthday. a day to stand up and be proud, even if you're sitting down. brian mooar, nbc news, washington. >>> there's another celebration today at the white house. it's malia's birthday. she turned 13. >> she will celebrate tonight with hundreds of troops and their families as they attend a special barbecue and a u.s. concert on the south lawn. malia's younger sister, sasha, turned 10, last month. >>> vice president joe biden made his mark on the world of twitter today. the vp sent out his first tweet just past 11:30 this morning. it read, vp and doctor b, hope you take time to think about our troops and military families this independence day. happy july 4th from ovp, joining forces. dr. b refers to his wife jill. biden's user name is @vp, all part of an increasing focus on social media. on wednesday, preside